Device for controlling oscillating circuits



June 21, 1949. c. A. WILEY DEVICE FOR CONTROLLING OSCILLATING CIRCUITS Filed March 15, 1943 5 HMPUHEE F/a Z. 4 Fla. 3.

Jauzc: a! 4.0. on 0G CARL- I/V/LEY w, 241/ zQ z/M/e Patented June 21, 1949 DEVICE FOR CONTROLLING OSCILLATING CIRCUITS Carl A. Wiley, Xenia, Ohio Application March 15, 1943, Serial No. 479,160

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to frequency modulated radio apparatus, and more particularly to a method with novel means for controlling the frequency of an oscillating circuit by varying the capacitive reactance thereof.

An object of this invention is to provide a simple, structurally strong, electrically effective and stable, and thermally stable, extremely high dielectric device of low power factor for varying the capacitive reactance of an oscillating circuit to enable frequency modulation, in a simple circuit in response to a variable control voltage loading of the dielectric.

The "dielectric constant of certain dielectrics, such as the titanates, especially barium titanate, change, with the values of direct current voltages applied thereto. In my invention such dielectrics are employed in a condenser of the oscillating circuit whereby the capacity of the condenser can be varied to control the frequency of the oscillating circuit by applying various current voltages to the condenser. These voltages may be audio frequencies created by a microphone or the like. I

Figure 1 is a schematic diagram of my invention as applied to a conventional tuned plate tuned grid circuit.

Figure 2 is a schematic diagram of my invention applied to a conventional Hartley circuit.

Figure 3 illustrates the means whereby the invention may be employed for telegraph transmission.

In accordance with the invention, the oscillating circuit can be of any well known type having a tuned frequency controlling circuit including a condenser I provided with a dielectric 2 formed from barium titanate or the like, and a tuning inductance 3. A choke I is provided to prevent high frequency current in the tuning circuit from flowing through the source of direct current potential, and a blocking condenser 5 is included in the circuit to prevent the inductance from acting as a direct current short across the condenser I. The direct current potential is provided by an amplifier 6 which receives its excitation from a microphone 'l. a

The dielectric 2 of condenser l is formed from barium titanate mixed with steatite as a binder. It has been found that a dielectric formed from barium titanate, and also other titanates, has a "dielectric constan which varies with the value of direct current impressed thereon. Such substances have been determined to have dielectric constants" varying from 78 to 1'70, depending upon Whether the impressed direct current is perpendicular or parallel to a given axis. Ex-

perimental data indicate that the interaction forces between the titanat molecules is such that the molecules were region of several thousand molecules are lined up so their dipole moments all have the same sense. In analogous character to the case of ferromagnetic materials where the magnetic dipoles in a region of about the same size have the same sense, the resulting domain is much more easily aligned than the individual molecules, resulting in a very high dielectric constant. v

The voice currents impressed on the condenser l by modulator 6 change the frequency of the sharply tuned grid circuit of the tuned plated tuned grid circuit. The plate circuit having a broad response tank circuit, varies infrequency according to variations in the grid circuit.

Figure 2 illustrates the invention applied to a Hartley circuit, in which variations in the D. C. potential, affect the capacity of condenser l thereby varying the frequency. A source of current 66 is provided.

Figure 3 illustrates the invention applied to telegraphy. The source of A. C. or D. C. potential is applied by a key It) to the condenser l which may be the condenser I of either Figure 1 or Figure 2 or the frequency control condenser of any circuit. When D. C. is employed, a shift in frequency is effected when the key is operated and when A. C. is employed an audio frequency modulation is effected upon depressing the key.

From the above description it will be seen that there has been provided a simple and eflective device for use in the indicated method of controlling the frequency of an oscillating circuit.

What is claimed is:

1. In a system having a first circuit with which a capacitance responsive to a voltage load variation to vary its time constant is cooperatively associated, a local loading circuit to said capacitance substantially independent of the first circuit, and control means in the last-named circuit to vary the loading on said capacitance; that improvement wherein the capacitance includes electrodes and an interposed dielectric consisting of a body of titanate substance responsive to changes in relative potentials of its electrodes by internal molecular change to vary its dielectric constant.

2. In a resonant circuit including a tuning capacitance, wherein is included a load-responsive capacitance responsive to a voltage load thereacross to vary its time constant, a local loading circuit for the last-named capacitance substantially independent of the said resonant circuit, and means to vary the voltage load in said local circuit on said load-responsive capacitance whereby to modulate the frequency of the resonant circuit; that improvement wherein a dielectric is included in said load-responsive capacitance consisting of a body mainly of a titanate substance responsive to changes in relative potentials of operatively associated electrodes to vary the molecular condition within the body of th dielectric so as to alter its dielectric constant.

3. The structure of claim 1 wherein said dielectric in the load-responsive capacitance is comprised substantially completely of barium titanate.

4. The structure of claim 1 wherein said dielectric has an essential amount of barium titanate.

5. In an oscillator having a tuned circuit including capacitanc and wherein at least a part of the capacitance is a load-responsive capacitance constructed to vary its time constant in response to changes in load thereon, a local loading circuit constructed to apply a voltage load across said load responsive capacitance, and means to vary the load in said local circuit; that improvement wherein said load-responsive capacitance includes opposed electrodes and an interposed dielectric consisting essentially of barium titanate.

6. In a capacitative circuit wherein the time constant of the circuit is varied by the inclusion of a capacitor having opposed electrodes and an interposed dielectric variable in dielectric constant under variation of electrical loading thereof, and wherein the dielectric is subjected to a variable control voltage loading in an auxiliary circuit, and said control voltage varied to produce required variations of the time constant of said first named circuit; the improvement comprising a dielectric in said capacitor consisting of a body substantially of barium titanate.

' CARL A. WILEY.

REFERENCES CITED The following references are of record in the tile 01 this patent:

" UNITED STATES PATENTS Number Name Date 1,777,410 Jones Oct. 7, 1930 1,917,394 Roberts July 11, 1933 2,032,620 Langmuir Mar. 3, 1936 2,071,452 Block Feb. 23, 1937 2,071,564 Nicolson Feb. 23, 1937 2,106,039 Safiord Jan. 18, 1938 2,115,666 Dom Apr. 26, 1938 2,165,819 Albers-Schonberg July 11, 1939 2,182,377 Guanella Dec. 5, 1939 2,226,299 Albers-Schonberg Dec. 24, 1940 2,243,921 Rust et a1 June 3, 1941 2,277,733 Wainer et al Mar. 31, 1942 2,277,734 Wainer et al Mar. 31, 1942 2,306,555 Mueller Dec. 29, 1942 2,368,643 Crosby Feb. 6, 1945 2,369,327 Wainer et al Feb. 13, 1945 2,377,910 Wainer et al June 12, 1945 FOREIGN PATENTS Number Country Date 467,443 Great Britain June 16, 1937 

